JP2009214389A - Flow casting device, solution film forming equipment and solution film forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of air entrainment in a flow casting process. <P>SOLUTION: The peripheral surface 32c is made to travel in the X-direction by the rotation of a drum body 32a. A flow casting die 30 discharges the dope 21 on the peripheral surface 32c. The dope 21 forms flow casting beads 40 from a flow-out port 30a to the peripheral surface 32c and then forms a flow casing film 33 on the peripheral surface 32c. A peel-off roller 34 peels-off the flow casting film 33 from the peripheral surface 32c and the flow casting film is sent to a tenter as a wet film 47. The peripheral surface 32c after the flow casting film 33 is peeled off is butted to a sponge roller 76. Droplets formed on the peripheral surface 32c is absorbed by the sponge roller 76. In a drying wind chamber 75, drying wind is blown to the peripheral surface 32c to vaporize the droplets remaining on the peripheral surface 32c and the formation of the droplets on the peripheral surface 32c is suppressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a casting apparatus, a solution casting apparatus, and a solution casting method.

  Polymer films (hereinafter referred to as “films”) are widely used as optical functional films because of their features such as excellent light transmittance, flexibility, and light weight thinning. Among them, cellulose ester films using cellulose acylate have toughness and low birefringence, and therefore, the composition of liquid crystal display devices (LCDs) that have recently expanded in the market including photographic photosensitive films. It is used as a protective film or an optical compensation film for a polarizing plate as a member.

  Main film production methods include a melt extrusion method and a solution casting method. The melt extrusion method is a method in which a polymer is heated and dissolved as it is, and then extruded with an extruder to produce a film, which has features such as high productivity and relatively low equipment cost. However, it is difficult to adjust the film thickness with high precision, and since fine lines (die lines) can be formed on the surface of the film, a high quality film that can be used for an optical functional film is manufactured. Is difficult. On the other hand, in the solution casting method, a cast film formed by casting a polymer solution containing a polymer and a solvent on a support has self-supporting properties, and then peeled off from the support. In this method, a wet film is formed, and the wet film is further dried to form a film. Compared with the melt extrusion method, it is superior in optical isotropy and thickness uniformity, and can obtain a film with less contained foreign substances. Therefore, optical functional films for LCD applications are mainly produced by a solution casting method. ing.

  This solution casting method prepares a polymer solution (hereinafter referred to as a dope) in which a polymer such as cellulose triacetate is dissolved in a mixed solvent containing dichloromethane or methyl acetate as a main solvent. Furthermore, a predetermined additive is mixed with this dope to prepare a casting dope. Using a casting die, the casting dope is discharged onto a support such as a casting drum or an endless band to form a casting film on the support (hereinafter referred to as a casting step). After the cast film is cooled on the support and becomes self-supporting, it is peeled off from the support as a film (hereinafter referred to as a wet film), and the wet film is dried as a film. Wind up.

  In order to meet the remarkable growth in demand for liquid crystal display devices and the like in recent years, establishment of a solution casting method with high production efficiency is required. From the viewpoint of improving the production efficiency, the casting process becomes rate-limiting when the solution casting method is speeded up. However, in the casting process, the accompanying wind that flows toward the casting bead is generated in the vicinity of the surface of the support due to the running of the support. Therefore, the accompanying wind flows as the running speed of the support increases. It enters between the extended bead and the support surface (hereinafter referred to as air entrainment). When air entrainment occurs in the casting process, unevenness in thickness occurs in the finally manufactured film.

As a method for suppressing air entrainment, there is a method (Patent Document 1) in which electrostatic application is performed between a casting bead and a support in a casting process.
JP 2001-113544 A

  However, in the casting process, moisture and solvent contained in the atmosphere around the support are condensed and appear as droplets on the support. Even if electrostatic is applied between the support in a state where the droplets are generated and a new casting bead, uneven charging occurs due to the droplets, and electrostatic attraction between the casting bead and the support is generated. As a result, the occurrence of air entrainment cannot be sufficiently suppressed.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a casting apparatus, a solution casting apparatus, and a solution casting method that can suppress the occurrence of uneven film thickness.

  The present invention discharges a dope from a casting die to a support that runs endlessly, forms a casting film on the support, and peels off the support after the casting film has self-supporting properties. In the casting apparatus, the grounding means for electrically grounding the support and the support after the casting film is peeled off and before the dope is discharged are charged by discharging. And a droplet removing device that removes droplets on the support after the casting film has been peeled off and before being charged by the charging device. To do.

  It is preferable that the droplet removing device has a dry air chamber for applying a dry air to the support. Moreover, it is preferable that the droplet removing device includes a sponge member that absorbs the droplet. Furthermore, it is preferable that the support is provided with an electrical insulating portion that discharges the dope and forms the cast film.

  The solution casting apparatus of the present invention includes the above casting apparatus, a stripping apparatus that strips the casting film from the support, and a drying apparatus that dries the stripped casting film to form a film. It is characterized by providing.

  The solution casting method of the present invention is characterized in that the casting film is formed on the support using the casting apparatus, and the casting film is peeled off and dried to form a film.

  According to the casting apparatus of the present invention, the support from which the cast film has been peeled off is discharged, and after charging, a new dope is discharged. Therefore, the support is uniformly charged and cast by electrostatic attraction. The bead and the support can be brought into close contact with each other, and as a result, the occurrence of air entrainment can be suppressed. Therefore, according to the solution casting apparatus and the solution casting method of the present invention, a film can be produced while suppressing the occurrence of thickness unevenness.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments listed here.

  As shown in FIG. 1, the film production line 10 includes a stock tank 11, a casting chamber 12, a pin tenter 13, a clip tenter 14, a drying chamber 15, a cooling chamber 16, and a winding chamber 17.

  The stock tank 11 is provided with a stirring blade 11b rotated by a motor 11a and a jacket 11c, and a casting dope (hereinafter referred to as dope) 21 as a raw material for the film 20 is stored therein. . In the stock tank 11, the temperature of the dope 21 is adjusted to 25 to 35 ° C. by flowing a heat transfer medium inside the jacket 11c, and the stirring blade 11b is rotated by the motor 11a. Thereby, the dope 21 is kept homogeneous while suppressing aggregation of polymers and the like.

  A pump 25 and a filtration device 26 are provided downstream of the stock tank 11. An appropriate amount of the dope 21 is appropriately sent from the stock tank 11 to the filtering device 26 by the pump 25 and filtered to remove impurities in the dope 21.

  In the casting chamber 12, as a casting apparatus, a casting die 30 that is an outflow means of the dope 21, a casting drum 32 that is an endless support, and a casting film 33 is peeled off from the casting drum 32. A roller 34, a temperature adjusting device 35 for adjusting the internal temperature of the casting chamber 12, and a decompression chamber 36 as decompression means are provided.

  As shown in FIG. 2, an outlet 30 a through which the dope 21 flows out is provided at the tip of the casting die 30. The outflow port 30a casts the dope 21 onto the casting drum 32 disposed below the outlet 30a. The material of the casting die 30 is formed of a material having high corrosion resistance against a mixed solution of an electrolyte aqueous solution, methylene chloride, methanol, and the like, and a low coefficient of thermal expansion. Moreover, it is preferable to use the finishing precision of the wetted surface of the casting die 30 with a surface roughness of 1 μm or less and a straightness of 1 μm / m or less in any direction. By using such a casting die 30, a casting film 33 without streaks and unevenness can be formed on the casting drum 32.

  As shown in FIG.1 and FIG.2, the casting drum 32 has the drum main body 32a formed in a substantially cylindrical shape, and the axis | shaft 32b. The drum body 32a is rotated about a shaft 32b by a driving device (not shown). By this drive device, the peripheral surface 32c of the drum body 32a rotates so as to travel at a predetermined traveling speed (10 to 300 m / min) in a predetermined traveling direction (hereinafter referred to as X direction). The peripheral surface 32c is chrome-plated and has sufficient corrosion resistance and strength. A heat transfer medium circulation device 37 is attached to the casting drum 32. The heat transfer medium maintained at a desired temperature by the heat transfer medium circulation device 37 passes through the heat transfer medium flow path in the casting drum 32, so that the temperature of the peripheral surface 32c of the casting drum 32 is increased. It can be kept in a desired range (−20 ° C. to 0 ° C.).

  In the casting process, the dope 21 flows out from the outlet 30 a toward the peripheral surface 32 c of the casting drum 32. The dope 21 forms a casting bead 40 from the outlet 30a to the peripheral surface 32c. On the traveling peripheral surface 32 c, the dope 21 flows and a casting film 33 is formed. The casting film 33 is conveyed at a predetermined speed in the X direction by the rotation of the casting drum 32. In this way, by continuously flowing out the dope 21 to the traveling peripheral surface 32c, the elongated casting film 33 is formed on the peripheral surface 32c.

  The decompression chamber 36 is disposed on the upstream side in the X direction with respect to the casting die 30 and decompresses the back side of the casting bead 40 with a negative pressure. By reducing the pressure on the back side of the casting bead 40, the adhesion between the circumferential surface 32c and the casting bead 40 is improved, so that air is mixed between the casting film 33 and the circumferential surface 32c. Can be prevented. Here, the back side refers to one side of the casting bead 40 located on the upstream side in the X direction. Under a control unit (not shown), the decompression chamber 36 can decompress the back side of the casting bead 40 in the range of −1500 Pa to −10 Pa. As shown in FIG. 1, the casting film 33 having self-supporting property by cooling on the casting drum 32 is peeled off from the casting drum 32 by the peeling roller 34 to become a wet film 47. Note that the decompression chamber 36 may be omitted.

  As shown in FIG. 1, the internal temperature of the casting chamber 12 is adjusted by the temperature control equipment 35 so as to be substantially constant within a predetermined range. The internal temperature of the casting chamber 12 is preferably 10 ° C or higher and 30 ° C or lower. In the casting chamber 12, a condenser (condenser) 48 for condensing and recovering the vaporized solvent and a recovery device 49 for recovering the condensed and liquefied solvent are provided. The organic solvent condensed and liquefied by the condenser 48 is recovered by the recovery device 49. The solvent is regenerated as a solvent for preparing a dope after being regenerated by a regenerator. With this recovery device 49, the condensation point of the solvent in the casting chamber 12 is maintained at −20 ° C. or higher and 25 ° C. or lower. When the condensation point in the casting chamber 12 is less than −20 ° C., the solvent is likely to evaporate, so that plate-out is likely to occur, and when the condensation point exceeds 25 ° C., it is not preferable. It is not preferable because the condensation of the solvent that causes the failure of the state is likely to occur on the peripheral surface 32c. Here, the condensation point is a temperature at which condensation of the solvent contained in the atmosphere starts.

  A pin tenter 13 that dries the wet film 47 to form the film 20 and a clip tenter 14 that stretches while drying the film 20 are provided downstream of the casting chamber 12. In the pin tenter 13, a large number of pins are inserted and fixed at both end portions of the wet film 47, and then drying is promoted while the wet film 47 is conveyed to form the film 20. Then, the film 20 still containing the solvent is fed into the clip tenter 14.

  In the clip tenter 14, drying is promoted while the film 20 is transported after the both ends of the film 20 are sandwiched by a number of clips that run endlessly by the movement of the chain. At this time, the film 20 is stretched by expanding the width of the facing clip and applying tension in the width direction of the film 20. Thus, by the stretching process in the width direction of the film 20, the molecules in the film 20 are oriented, and desired optical properties such as retardation can be imparted to the film 20. The clip tenter 14 may be omitted.

  The film 20 sent out from the clip tenter 14 is cut at both end portions by the edge-cutting device 51. The edge-cutting device 51 is provided with a crusher 52. Here, both end portions of the film 20 are cut and then fed into the crusher 52 to be crushed. The crushed film strip is reused as a raw material dope.

  The film 20 whose both end portions are cut by the edge cutting device 51 is sent to the drying chamber 15. The drying chamber 15 is provided with a number of rollers 53 and an adsorption / recovery device 54. The film 20 is conveyed through the drying chamber 15 by a roller 53. The film 20 dried in the drying chamber 15 is sent to the cooling chamber 16, cooled to 30 ° C. or less, and then sent to the winding chamber 17. Further, a forced static elimination device (static elimination bar) 55 is provided downstream of the cooling chamber 16. Furthermore, in the present embodiment, a knurling roller 56 is provided on the downstream side of the forced static elimination device 55.

  Inside the winding chamber 17, there are provided a winder 57 and a press roller 58 that rotate the core 57 a to wind the film 20 around the core 57 a. The film 20 sent to the winding chamber 17 is wound around the winding core 57 a while being pressed by the press roller 58.

  Next, the details of the casting chamber 12 will be described. The casting chamber 12 is divided into a casting part 63 and a stripping part 64 by partition plates 61 and 62. The partition plate 61 is provided between the peeling roller 34 and the decompression chamber 36 in the X direction, and the partition plate 62 is provided between the casting die 30 and the peeling roller 34 in the X direction. The partition plates 61 and 62 are formed so as to extend from the inner wall surface of the casting chamber 12 toward the casting drum 32 and have their tips close to the peripheral surface 32c. In addition, a labyrinth groove is provided at the distal end portion of the partition plates 61 and 62 on the peripheral surface 32c side. Due to the partition plates 61 and 62, the casting part 63 has an airtight structure.

  The casting chamber 12 is provided with an insulating support portion 67 made of an electrical insulator. The casting drum 32 is attached to the insulating support portion 67 so that the drum body 32a is rotatable. Thereby, the peripheral surface 32c of the drum main body 32a is electrically ungrounded.

  As shown in FIGS. 1 and 2, the casting chamber 12 is provided with an electrode rod 70, an oxygen concentration meter 71, a nitrogen supply unit 72, a controller 74, a drying air chamber 75, and a sponge roller 76. The oxygen concentration meter 71 measures the oxygen concentration in the casting part 63 under the control of the controller 74. Under the control of the controller 74, the nitrogen supply unit 72 supplies nitrogen gas to the casting unit 63 according to the oxygen concentration measured by the oxygen concentration meter 71. Thereby, since it becomes possible to maintain the oxygen concentration of the casting part 63 in a predetermined | prescribed range, the fire and explosion by the discharge from the electrode stick | rod 70 or the surrounding surface 32c can be suppressed.

  The electrode rod 70 is disposed on the upstream side in the X direction of the decompression chamber 36 of the casting portion 63 so as to be close to the peripheral surface 32c. As shown in FIGS. 2 and 3, the electrode rod 70 is formed to extend in the width direction of the casting film 33 (hereinafter referred to as the Y direction). It is preferable to cover the electrode rod 70 with a chamber and partition the inside of the casting portion 63. Thereby, it is prevented that the solvent gas floating inside the casting part 63 adheres to the electrode rod 70 and the charging efficiency is lowered. In addition, it is preferable to provide a labyrinth seal at the lower end between the lower end of the chamber and the peripheral surface 32c.

  The sponge roller 76 is provided on the upstream side in the X direction of the electrode rod 70 of the casting portion 63. The sponge roller 76 has a shaft and a roller body that is rotatably provided on the shaft. The roller body is made of PVA sponge and is formed to extend in the Y direction. The sponge roller 76 is disposed such that the peripheral surface of the roller body is in contact with the peripheral surface 32c. The peripheral surface of the roller body is formed flat. In addition, you may provide the protrusion extended in the circumferential direction on the surrounding surface of a roller main body so that it may space apart in an axial direction. The top of the ridge is preferably formed in a circular arc shape in cross section.

  The drying air chamber 75 is provided on the casting portion 63 on the upstream side in the X direction of the electrode rod 70 and on the downstream side in the X direction of the sponge roller 76 so as to cover the peripheral surface 32c. Under the control of the controller 71, the drying air chamber 75 applies the drying air adjusted to satisfy a predetermined condition to the peripheral surface 32c. As the drying air, it is preferable to use a gas having a low dew point or a low condensation point of the solvent. The dew point of the drying wind and the condensation point of the solvent are lower than the temperature TS of the peripheral surface 32c, and specifically, it is preferably (TS-20) ° C. or higher and (TS-10) ° C. or lower. As the gas used for the drying air, nitrogen gas, carbon dioxide gas, active gas, or a mixed gas obtained by mixing them may be used.

  Next, the operation of the film production line 10 configured as described above will be described. As shown in FIG. 1, the heat transfer medium circulation device 37 makes the temperature of the peripheral surface 32c of the drum body 32a substantially constant within a predetermined range. As shown in FIGS. 1 and 2, the controller 74 does not apply a voltage to the electrode rod 70, and nitrogen is supplied so that the oxygen concentration in the casting part 63 is within a predetermined range via the nitrogen supply part 72. Is supplied to the casting part 63. Thereby, the controller 74 maintains the oxygen concentration in the casting part 63 within a predetermined range (less than 10% by weight). When the oxygen concentration in the casting part 63 falls within a predetermined range, the controller 74 starts applying a voltage to the electrode rod 70. By applying a voltage to the electrode rod 70, a discharge occurs between the electrode rod 70 and the peripheral surface 32c. Since the drum main body 32a is electrically ungrounded, the peripheral surface 32c is charged by this discharge.

  The drum body 32a rotates around the shaft 32b, and the peripheral surface 32c travels in the X direction. The dope 21 discharged from the outlet 30a toward the peripheral surface 32c forms a casting bead 40 from the outlet 30a to the peripheral surface 32c. The charged peripheral surface 32 c causes electrostatic induction or dielectric polarization in the dope 21 forming the casting bead 40, so that the back surface side of the casting bead 40 and the peripheral surface 32 c are in close contact with each other. And the casting film 33 is formed in the surrounding surface 32c, and the casting film 33 has self-supporting property by cooling gelation. The casting film 33 is conveyed in the direction X by the travel of the peripheral surface 32 c, is peeled off from the peripheral surface 32 c by the stripping roller 34, and is sent to the tenter 13 (see FIG. 1) as a wet film 47.

  Since the surface temperature of the peripheral surface 32c is set to 0 ° C. or less, droplets containing water droplets and a solvent are easily generated on the peripheral surface 32c after the casting film 33 is peeled off. When discharge is performed on the peripheral surface 32c where such droplets remain, charging unevenness occurs in which the peripheral surface 32c is not uniformly charged.

  In the present invention, since the sponge roller 76 comes into contact with the peripheral surface 32c after the casting film 33 is peeled off, the droplet generated on the peripheral surface 32c is absorbed by the roller body made of sponge, and as a result, the peripheral surface 32c. The generated droplets are removed. Further, since the drying air chamber 75 applies the drying air to the peripheral surface 32c, it is possible to vaporize the liquid droplets remaining on the peripheral surface 32c and to suppress the condensation of the liquid droplets on the peripheral surface 32c. Thereafter, the peripheral surface 32c is discharged again, and a new dope 21 is discharged onto the charged peripheral surface 32c. Therefore, the unevenness of charging on the peripheral surface 32c is suppressed, and the casting bead 40 and the peripheral surface 32c are caused by electrostatic attraction. Can be adhered more reliably and uniformly. Therefore, according to the present invention, it is possible to suppress the occurrence of air entrainment, and thus it is possible to manufacture a film while suppressing the occurrence of thickness unevenness.

  In order to effectively suppress air entrainment, the potential V of the peripheral surface 32c of the casting drum 32 is preferably 0.1 kV ≦ | V | ≦ 3 kV. This potential V can be easily controlled by adjusting the amount of discharge from the electrode rod 70. When V is less than 0.1 kV, since only a weak force can be applied between the casting bead 40 and the casting drum 32, it may be difficult to suppress air entrainment. On the other hand, if V exceeds 3 kV, the charging amount of the casting drum 32 may be too large and the bead may sway, and the charging amount may be uneven in the width direction of the casting drum 32. is there. Further, if V exceeds 3 kV, dielectric breakdown may occur on the peripheral surface 32c.

  In the above embodiment, the sponge roller 76 is provided on the upstream side in the X direction of the drying air chamber 75 in the casting portion 63, but the present invention is not limited to this. For example, a sponge roller 76 may be provided on the upstream side of the electrode rod 70 in the X direction and on the downstream side of the dry air chamber 75 in the X direction. Further, the drying air chamber 75 and the sponge roller 76 may be provided in the peeling portion 64 on the downstream side in the X direction of the peeling roller 34. In addition, any one of the drying air chamber 75 and the sponge roller 76 may be provided.

  In the above embodiment, a similar partition plate 79 may be provided between the casting die 30 and the partition plate 62 in the X direction. As described above, the upstream and downstream sides of the casting die 30 and the decompression chamber 36 in the X direction are separated by the partition plates 62 and 79, so that the casting bead 40 vibrates due to the accompanying wind generated along the traveling of the peripheral surface 32c. Can be suppressed.

  In the above embodiment, the peripheral surface 32c is charged using the electrode rod 70. However, the present invention is not limited to this, and an ion wind spray device 81 as shown in FIG. 4 may be used. The ion wind spray device 81 includes a duct, an electrode provided inside the duct, and a blowout port 82 that is an outlet of the duct. The electrode is discharged by a control unit (not shown), and an ion wind is generated from the wind passing through the inside of the duct by this discharge. The outlets 82 are arranged in the Y direction so as to face the peripheral surface 32c. The polarity of the ion wind may be opposite to the polarity charged on the peripheral surface 32c. Moreover, you may apply the ion wind produced | generated from the dry wind to the surrounding surface 32c. In this case, the drying air chamber 75 and the sponge roller 76 may be omitted.

  Further, as shown in FIG. 5, it is preferable to provide an electrical insulating layer 90 on the peripheral surface 32c of the drum body 32a. By discharging the peripheral surface 32c through the electrical insulating layer 90, a dendritic discharge path along the surface of the electrical insulating layer 90 can be formed, and the peripheral surface 32c can be easily charged. Furthermore, a metal support layer 91 may be provided on the electrical insulating layer 90 so as to be electrically insulated from the drum body 32a, and the casting film 33 may be formed by casting the dope 21 on the support layer 91. . In this case, the insulating support 67 may be omitted. The material for forming the support layer 91 is preferably the same as that of the drum body 32a and the peripheral surface 32c.

  The electrical insulating layer 90 may be formed by melt-depositing an insulating material. The insulating material is not particularly limited, and examples thereof include ceramics, PTFE, and plastic. The ceramic includes alumina, zirconia, chromium oxide, titania, or a mixture including at least any two of them. The formation method, film thickness, and the like are not particularly limited, but it is preferable that the film be formed so as to have a uniform film thickness over the entire peripheral surface 32c of the casting drum 32. The electrical insulating layer 90 of this embodiment is a film formed by melting and bonding ceramics mainly composed of alumina. The support layer 91 may also be formed using a method similar to that for the electrical insulating layer 90.

  The electrical insulating layer 90 is preferably not a single layer structure but a multilayer structure. For example, it is more preferable to have a multilayer structure including a first layer 90a and a second layer 90b that overlaps the inside of the first layer 90a and is thicker than the first layer 90a. The first layer 90a preferably has a smooth exposed surface (hereinafter referred to as an exposed surface) in order to make the surface of the casting film 33 in contact with the first layer 90a as smooth as possible. This is because if the surface of the casting film 33 is rough, the surface of the resulting film 20 (see FIG. 1) often becomes rough. In order to form the surface of the first layer 90a made of ceramics smoothly, it is preferable to use ceramics having a small particle size as a raw material. The same applies when PTFE is used instead of ceramics as the material of the first layer 90a.

  The smaller the particle size of the ceramic or PTFE used for the first layer 90a, the easier it is for the first layer 90a to crack or to be formed with cracks. This tendency increases as the first layer 90a becomes thicker. Therefore, the second layer 90b is provided inside the first layer 90a. The second layer 90b is formed of ceramic or PTFE having a larger particle size than the material of the first layer 90a. As a result, the electrical insulating layer 90 is formed smoothly without cracking, and cracks are less likely to occur even after long-term use. The electrical insulating layer 90 has a multi-layer structure of the first layer 90a and the second layer 90b made of the material as described above, so that the surface is smooth and the electrical insulation is large. Can do. A plurality of the second layers 90b may be provided.

  A plurality of electrode bars 70 may be arranged in the X direction. Thereby, the peripheral surface 32c of the casting drum 32 can be charged uniformly.

  The method for charging the casting drum 32 is not limited to the above embodiment, and examples include a method using a friction member. In this case, the casting drum 32 can be charged by bringing the friction member into contact with the casting drum 32 and generating static electricity. Examples of the friction member include, but are not particularly limited to, a metal rod, a belt, a rubber product, and the like with a cloth wrapped around the surface, but the surface of the casting drum 32 is not scratched as much as possible. It is preferable that the pressure at the time of contact is appropriately adjusted while selecting the member.

  In addition, you may provide a static elimination brush in the X direction upstream of the electrode rod 70 of the casting part 63. FIG. The neutralizing brush is provided so as to extend in the Y direction. Further, the static elimination brush has stainless steel bristle that is electrically grounded, and is arranged so that the bristle contacts the peripheral surface 32c.

  The nitrogen supply unit 72 may supply carbon dioxide gas or inert gas to the casting unit 63 in addition to nitrogen gas, or supply a mixed gas or the like obtained by mixing these gases to the casting unit 63. Also good.

  According to the present invention, it is possible to produce a film 20 that is at least 100 m in the transport direction and 1400 to 2500 mm in the width direction. However, the present invention is effective even when it is larger than 2500 mm. Although the film thickness of the completed film 20 is not specifically limited, It is preferable that it is 20-500 micrometers. More preferably, it is 30-300 micrometers, Most preferably, it is 35-200 micrometers, but the effect of this invention can be acquired even when the film thickness of the film 20 is as thin as 15-100 micrometers.

  It is preferable that a solvent supply device (not shown) is attached to the end of the discharge port of the casting die 30 to supply a desired solvent to both ends of the casting bead 40 in the Y direction. As the solvent, a solvent capable of dissolving the dope is preferably used. For example, a mixture in which 86.5 parts by weight of dichloromethane, 13 parts by weight of methanol, and 0.5 parts by weight of n-butanol are mixed. It is done. Thereby, since dope does not dry locally and solidify, a bead can be formed stably. In addition, since the possibility that the solidified dope is mixed into the bead or the casting film 33 as a foreign substance is reduced, the film 20 having no defect and having high transparency can be obtained. Moreover, when supplying the above mixture, the supply amount is in the range of 0.1 to 1.0 mL / min for each side of the end of the discharge port using a pump having a pulsation rate of 5% or less. It is preferable to supply so that it becomes.

  Furthermore, when casting dopes, simultaneous lamination co-casting in which two or more types of dopes are simultaneously co-cast and laminated, or sequential lamination co-casting in which multiple dopes are sequentially co-cast and laminated It can be performed. In addition, you may combine both casting. When performing simultaneous lamination and co-casting, a casting die to which a feed block is attached may be used, or a multi-manifold casting die may be used. However, it is preferable that at least one of the thickness of the layer on the air surface side and the thickness of the layer on the support side is 0.5 to 30% of the thickness of the entire film of the film composed of multiple layers by co-casting. . In addition, when performing simultaneous lamination and co-casting, it is preferable that the high-viscosity dope is enveloped by the low-viscosity dope when the dope is cast from the die slit to the support, and is formed from the die slit to the support. Of the casting beads, the dope in contact with the outside world preferably has a higher alcohol composition ratio than the inner dope.

  The present invention can also be applied to a casting apparatus that uses a casting band that moves over a rotating roller instead of the casting drum 32.

  Next, the polymer and solvent according to the present invention will be described.

  It is preferable to use cellulose ester as the polymer because a film with high transparency can be obtained. Examples of the cellulose ester include lower fatty acid esters of cellulose such as cellulose triacetate, cellulose acetate propionate, and cellulose acylate butyrate. Especially, it is preferable to use a cellulose acylate from the height of transparency, and it is especially preferable to use triacetylcellulose (TAC). The dope used in the present embodiment includes triacetyl cellulose (TAC) as a polymer. Thus, when using TAC, it is preferable that 90 weight% or more of TAC is a particle | grain of 0.1-4 mm. In addition, the polymer component of dope is not limited to a cellulose ester, What is necessary is just a well-known thing which can be dissolved in a solvent and can make dope.

As said cellulose acylate, in order to obtain a film with higher transparency, it is preferable that the substitution degree of the acyl group to the hydroxyl group of cellulose satisfies all of the following formulas (a) to (c). A and B in the following formula represent the substitution degree of the acyl group with respect to the hydrogen atom in the hydroxyl group of cellulose. Specifically, A is the substitution degree of the acetyl group, and B has 3 to 22 carbon atoms. The degree of substitution of the acyl group.
(A) 2.5 ≦ A + B ≦ 3.0
(B) 0 ≦ A ≦ 3.0
(C) 0 ≦ B ≦ 2.9

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio at which the hydroxyl group of cellulose is esterified at each of the 2-position, 3-position and 6-position. The degree of substitution is 1 in the case of 100% esterification.

  The total degree of acylation substitution, that is, the value of DS2 + DS3 + DS6 is preferably 2.00 to 3.00, more preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88. Further, the value of DS6 / (DS2 + DS3 + DS6) is preferably 0.28 or more, more preferably 0.30 or more, and particularly preferably 0.31 to 0.34. Here, DS2 is a ratio in which the hydrogen of the hydroxyl group at the 2-position in the glucose unit is substituted with an acyl group, and DS3 is a ratio in which the hydrogen of the hydroxyl group at the 3-position in the glucose unit is substituted with an acyl group. DS6 is the ratio in which the hydrogen of the 6-position hydroxyl group is replaced by an acyl group in the glucose unit.

  Only one kind of acyl group may be used for cellulose acylate, or two or more kinds of acyl groups may be used. When two or more kinds of acyl groups are used, it is preferable that one of them is an acetyl group. The sum of the degree of substitution of hydroxyl groups at the 2nd, 3rd and 6th positions by acetyl groups is DSA, and the sum of the degree of substitution of the hydroxyl groups at the 2nd, 3rd and 6th positions by acyl groups other than acetyl groups When DSB is DSB, the value of DSA + DSB is preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88.

  The DSB is preferably 0.30 or more, particularly preferably 0.7 or more. Further, 20% or more of DSB is preferably a substituent at the 6-position hydroxyl group, more preferably 25% or more, further preferably 30% or more, and particularly preferably 33% or more. Furthermore, the value of DSA + DSB at the 6-position of cellulose acylate is 0.75 or more, more preferably 0.80 or more, and particularly preferably cellulose acylate of 0.85 or more. When such cellulose acylate is used, a dope having excellent solubility can be prepared. In the case of using the cellulose acylate as described above, when a non-chlorine solvent is used, a dope having very excellent solubility, low viscosity, and excellent filterability can be prepared. .

  Cellulose, which is a raw material for cellulose acylate, may be obtained from either linter cotton or pulp cotton, but is preferably obtained from linter cotton.

  The acyl group having 2 or more carbon atoms of cellulose acylate may be an aliphatic group or an aryl group, and is not particularly limited. For example, cellulose alkylcarbonyl ester, alkenylcarbonyl ester, aromatic carbonyl ester, aromatic alkylcarbonyl ester and the like can be mentioned. Further, each may have a substituted group. Preferred examples of these include propionyl group, butanoyl group, pentanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, iso-butanoyl group , T-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a t-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and a propionyl group and a butanoyl group are particularly preferable. .

  The details of cellulose acylate that can be used in the present invention are described in paragraphs [0140] to [0195] of JP-A-2005-104148, and these descriptions also apply to the present invention. Can do.

  The solvent is preferably an organic compound that can dissolve the polymer used. However, in the present invention, the dope means a mixture obtained by dissolving or dispersing a polymer in a solvent, and therefore a solvent having low solubility with the polymer can also be used. Examples of the solvent that can be suitably used include aromatic hydrocarbons such as benzene and toluene, halogenated hydrocarbons such as dichloromethane, chloroform, and chlorobenzene, and alcohols such as methanol, ethanol, n-propanol, n-butanol, and diethylene glycol. , Ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate, ethyl acetate and propyl acetate, ethers such as tetrahydrofuran and methyl cellosolve, and the like. Two or more kinds of solvents may be selected from these solvents and mixed solvents may be used. Among these, use of dichloromethane is preferable because a dope having excellent solubility can be obtained, and the solvent in the cast film can be volatilized in a short time to form a film.

  As said halogenated hydrocarbon, a C1-C7 thing is used preferably. Furthermore, from the viewpoints of compatibility with the polymer, peelability which is an index of ease of peeling of the cast film peeled off from the support, mechanical strength of the film, optical properties, etc., dichloromethane has 1 to 5 carbon atoms. It is preferable to use one of these alcohols or a mixture of several alcohols. The content of alcohol is preferably 2 to 25% by weight, more preferably 5 to 20% by weight, based on the entire solvent. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc. Among them, it is preferable to use methanol, ethanol, n-butanol, or a mixture thereof.

  Recently, a solvent composition not using dichloromethane has been proposed in order to minimize the influence on the environment. For this purpose, ethers having 4 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms are preferable, and these are preferably used by being mixed appropriately. These compounds may have a cyclic structure, and compounds having two or more functional groups of ether, ketone, and ester, that is, -O-, -CO-, and -COO- are also used as a solvent. Can be used. In addition, the solvent may have another functional group such as an alcoholic hydroxyl group. In addition, when it has two or more types of functional groups, the carbon number should just be in the prescription | regulation range of the compound which has either functional group, and it does not specifically limit.

  Depending on the purpose, the dope may be added with various known additives such as a plasticizer, an ultraviolet absorber (UV agent), a deterioration preventing agent, a slipping agent, and a peeling accelerator. For example, as the plasticizer, phosphate plasticizers such as triphenyl phosphate and biphenyldiphenyl phosphate, phthalate plasticizers such as diethyl phthalate, and various known plasticizers such as polyester polyurethane elastomers are used. be able to.

  Moreover, it is preferable to add fine particles to the dope for the purpose of preventing adhesion between films or adjusting the refractive index. As the fine particles, a silicon dioxide derivative is preferably used. The silicon dioxide derivative in the present invention includes silicon dioxide and a silicone resin having a three-dimensional network structure. As such a silicon dioxide derivative, it is preferable to use an alkylated surface. Fine particles that have been subjected to a hydrophobization treatment such as an alkylation treatment are excellent in dispersibility in a solvent, so that a dope can be prepared without agglomeration between the fine particles, and a film can be produced. It is possible to produce a film with few state defects and high transparency.

  As described above, as the fine particles whose surface is alkylated, for example, Aerosil R805 (manufactured by Nippon Aerosil Co., Ltd.) which is commercially available as a silicon dioxide derivative having an octyl group introduced on its surface can be used. . In order to obtain a highly transparent film while ensuring the effect of adding fine particles, the fine particle content relative to the solid content of the dope is preferably 0.2% or less. Further, the average particle diameter is preferably 1.0 μm or less, more preferably 0.3 to 1.0 μm, and particularly preferably 0.4 to 0 so that the fine particles do not hinder the passage of light. .8 μm.

  As described above, in the present invention, it is preferable to prepare a dope using TAC as a polymer in order to obtain a highly transparent polymer film. In this case, it is preferable that the ratio containing TAC is 5 to 40% by weight with respect to the total amount of the dope after mixing the solvent, additives and the like. More preferably, the ratio containing TAC is 15 to 30% by weight, and particularly preferably 17 to 25% by weight. Moreover, it is preferable that the ratio in which an additive (mainly a plasticizer) is contained shall be 1 to 20 weight% with respect to the whole solid content including the polymer, other additives, etc. which are contained in dope.

  Note that various additives such as solvents, plasticizers, ultraviolet absorbers, deterioration inhibitors, slipping agents, release accelerators, optical anisotropy control agents, retardation control agents, dyes, release agents, and the like and fine particles are disclosed in JP-A-2005. No. 104148, paragraphs [0196] to [0516] describe in detail, and these descriptions can also be applied to the present invention. Further, it is a method for producing a dope using TAC. For example, materials, raw materials, additive dissolution methods and addition methods, filtration methods, defoaming, and the like are also disclosed in JP-A-2005-104148 [0517]. It is described in detail from paragraph to [0616] paragraph, and these descriptions can also be applied to the present invention.

[Experiment 1]
The film 20 was manufactured using the film manufacturing equipment 10 shown in FIG. The temperature inside the casting chamber 12 was always 35 ° C. using the temperature control equipment 35. Further, nitrogen gas was supplied into the casting chamber 12 to adjust the oxygen concentration to be always less than 10% by weight. The heat transfer medium supply device 37 maintained the temperature of the peripheral surface 32 c of the casting drum 32 at approximately −10 ° C. The casting die 30 has a discharge port formed of a slit having a width of 1.8 m and a jacket (not shown) for adjusting the internal temperature, and the temperature of the discharged dope 21 is about 36 ° C. It was. The pipes and the like serving as the dope flow path were all maintained at approximately 36 ° C. using a form having a temperature adjusting function. The drum main body 32a was rotated to run on the peripheral surface 32c. As shown in FIG. 2, the sponge roller 76 was brought into contact with the peripheral surface 32 c before discharging the dope 21, and the droplet generated on the peripheral surface 32 c was absorbed by the sponge roller 76. Thereafter, a high DC voltage was applied to the electrode rod 70 to discharge it, and the casting drum 32 was charged. The potential V of the peripheral surface 32c of the casting drum 32 was 1.0 kV.

  After feeding an appropriate amount of the dope 21 to the casting die 30, the dope 21 is discharged from the outlet of the casting die 30 onto the casting drum 32 continuously rotated as shown in FIG. A casting film 33 was formed on 32c. At this time, the pressure behind the bead was reduced to −600 Pa in the decompression chamber 36, and the discharge amount of the dope 21 was adjusted so that the thickness of the film 20 after drying was 80 μm.

  The casting film 33 that had become self-supporting due to cooling gelation was peeled off from the casting drum 32 while being supported by the peeling roller 34 to obtain a wet film 47. Next, the wet film 47 was sent to the tenter 13 and dried to obtain a film 20.

[Experiment 2]
The film 20 was manufactured in the same manner as in Experiment 1 except that instead of the sponge roller 76, a dry air was applied to the peripheral surface 32c using a dry air chamber 75.

[Experiment 3]
A film was produced in the same manner as in Experiment 1 except that the sponge roller 76 and the drying air chamber 75 were not used.

(Evaluation of thickness unevenness)
When the thickness unevenness of the obtained film was evaluated, the evaluation result in Experiments 1 and 2 was “◯”, and the evaluation result in Experiment 3 was “x”.

The film thickness unevenness evaluation was performed based on the following criteria using the relative standard deviation RSD of the film thickness as an index.
Relative standard deviation RSD is less than 5%. Excellent thickness uniformity. (○)
Relative standard deviation RSD was 5% or more and less than 10%. Although there was some thickness unevenness, there was no problem in use as an optical film. (△)
Relative standard deviation RSD is 10% or more. (×)

  The film thickness was measured at five points using an electronic micrometer manufactured by Anritsu Electric Co., Ltd. at 25 ° C. and 60 RH%. The relative standard deviation RSD (= deviation / average value × 100%) was calculated from the average value and deviation of the measured values.

It is explanatory drawing which shows the outline | summary of a film manufacturing line. It is a side view which shows the outline | summary of a casting part. It is a perspective view which shows the outline | summary of a casting drum, an electrode rod, a sponge roller, and a drying air chamber. It is a side view which shows the outline | summary of an ion wind spraying apparatus. It is sectional drawing of the drum main body and electric insulation film in the cross section containing the axis | shaft of a drum main body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Film production line 12 Casting chamber 30 Casting die 32 Casting drum 32a Drum main body 32b Shaft 32c Circumferential surface 32 Stripping roller 33 Casting film 40 Casting bead 63 Casting part 64 Stripping part 67 Insulation support part 70 Electrode Rod 75 Dry air chamber 76 Sponge roller

Claims (6)

In a casting apparatus in which a dope is discharged from a casting die onto a support that runs endlessly, a casting film is formed on the support, and the casting film is self-supporting and then peeled off from the support ,
Ungrounded means for electrically ungrounding the support;
A charging device that charges the support by discharging after the casting film has been peeled off and before the dope is discharged;
A droplet removing device for removing droplets on the support after the casting film has been peeled off and before being charged by the charging device;
A casting apparatus comprising:   The casting apparatus according to claim 1, wherein the droplet removing device has a dry air chamber that applies dry air to the support.   The casting apparatus according to claim 1, wherein the droplet removing device includes a sponge member that absorbs the droplet.   The casting apparatus according to any one of claims 1 to 3, wherein the support is provided with an electrical insulating portion that discharges the dope and forms the casting film. A casting apparatus according to any one of claims 1 to 4,
A stripping device for stripping the cast film from the support;
A drying device for drying the cast film peeled off to form a film;
A solution casting apparatus comprising:   A casting apparatus according to any one of claims 1 to 4, wherein the casting film is formed on the support, and the casting film is peeled off and dried to form a film. Solution casting method.

Images